1. Field of the Invention
This invention relates to devices for using the inherent resistivity of electrically conductive parts of a vehicle, e.g. operational control parts such as the brakes and control linkages, to generate heat in order to assist in keeping the parts operable in an ambient environment that tends to cause the parts to become inoperable due to icing.
2. Description of Related Art
While this invention can be used to prevent freeze-up due to icing of the brakes and other operational control parts of any type of vehicle having a sufficient source of electrical energy, such as automobiles, trucks, airplanes, helicopters, and railroad trains, the following discussions will focus on railroad train braking systems for illustration purposes only.
There are presently three basic brake systems for railroad cars. One system consists of block brakes, where the brake action is performed by cast iron blocks applied to the rolling surface of the wheels themselves. The second system consists of disc brakes, where two brake pads squeeze the wheel from each side to perform the brake action. A variation of this system is to have separate discs mounted on the shaft to which the brake pads are applied. The third system uses brake pads applied directly to the rail. This is mostly used for emergency braking. The latter two systems are also found in road vehicles and aircraft wheels.
All brakes operate with the principle of converting kinetic energy into heat for retardation of the vehicle. Most modern railroad cars also have anti-locking systems based on mechanically, electronically or microprocessor controlled devices.
All these systems appear to function well except in temperatures at or below freezing, i.e. less than 0.degree. C., in the presence of moisture. In such an environment the brakes tend to lock due to ice that is formed by condensation and/or precipitation, snow, ice and freezing of moisture on different parts of the bogie. To solve this problem, the following heating system is suggested to either prevent the ice from forming on vital parts or to prevent two parts from freezing together.